Electrical generating and control system



m {f E? Oct. 5, 1937. LA. HYLAND 2,095,134

ELECTRICAL GENERATING AND CONTROL SYSTEM I Filed June 28, 1934 E9 1UNSATURATED /7' k r I65 /6 A To LOAD MF SATURA TED 2/ I RECTIFIER RCT/F/ER RELAY 7 SATURATL'D 8 W RECTIFIER RECTIFIER INVENTOR. Lawrence A.Hy/and NEY.

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CURRENT 0 I VOLTAGE Patented oer. s, 1937 PATENT OFFICE ELECTRICALGENERATING AND CONTRO SYSTEM Lawrence A. Hyland, Washington, D. 0.,assignor to Eclipse Aviation Corporation, East Orange, N. J., acorporation of New Jersey Application June 28, 1934, Serial No. 732,938

2 Claims. (Cl. 171-223) The present application is a continuation inpart of my application Serial No. 585,013 filed January 6, 1932, andrelates to electrical generating systems and more particularly to thevoltage control thereof.

The novel system embodying the invention disclosed herein isparticularly adapted to be employed in places where it is inclose'proximity to radio receiving and transmitting apparatus as, forexample, on aircraft where all equipment is necessarily crowded due tolack of space.

Among the dimculties experienced heretofore with generating systems ofexisting designs were the eifects of electrical disturbances caused bytransients produced by commutator sparking, voltage regulator contactsparking, and other similar electrical disturbances. Even in electricalpower installations where alternating current is used for the receiverand transmitter of a radio signaling system, it has been the custom,heretofore, to employ a direct current generator in conjunction with analternator to supply the field current for the latter, thereby producingelectrical disturbances due to commutator sparking. Accordingly, one ofthe objects of the present invention is to provide a novel electricalgenerating and voltage control system wherein the foregoing diflicultiesare eliminated and by reason of which radio signaling is greatlyimproved.

Another object of the invention is to provide a novel electrical controlsystem for regulating the output voltage of any alternating current generator.

Another object is to provide a novel electrical generating systemwhereby va generated potential is maintained substantially constant.

Another object of the invention is to provide a novel electricalgenerating and voltage control system wherein sliding contacts, such ascommutators and collector rings, and make-andbreak devices, such ascontact voltage regulators, are eliminated and, hence, electricaldisturbances in radio receiving systems are prevented.

Another object is to provide a novel generating and control system ofthe foregoing type including an inductor alternator and a source ofelectric current whereby auxiliary field excitation may. be supplied tosaid alternator when the residual magnetism thereof is insuflicient forselfexcitation.

A further object is to provide in a generating system including avariable speed inductor alternator, a novel circuit arrangement wherebya portion of the output of said alternator is employed as fieldexcitation current therefor to maintain the output voltage substantiallyconstant.

A still further object is to provide in a system of the foregoing type,a novel circuit an'angement whereby a portion of the output current of 5said alternator is rectified and used to charge a battery, the latterbeing arranged to float on the output line of the alternator and to beemployed as a source of auxiliary field excitation to start thegenerating system when the residual mag- 10 netism of thealternator isinsufiicient for the purpose.

A still further object is to provide in a system of the foregoing type anovel circuit arrangement whereby two portions of the output current of15 said alternator are separately rectified to provide a main fieldexcitation and an auxiliary field excitation in opposition thereto andso arranged. that the auxiliary field excitation increases relativelyfaster than the main field excitation for a given increase in the outputvoltage of thealternator whereby the resultant field excitation isreduced in response to an increase in the output voltage so that thelatter is maintained substantially constant.

Still another object is to provide a novel generating and control systemwhich is relatively simple in circuit hook-up, in arrangement and innumber of parts, yet very eificient in operation and, therefore,particularly suitable for aircraft installations. i

The above and other objects and advantages of the invention will appearmore fully hereinafter from a consideration of the detailed descriptionwhich follows, when taken together with the accompanying drawing whereintwo embodiments of the invention are illustrated. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only and is not designed as a definition oi the limitsof the invention, reference being had for this purpose to the appendedclaims.

In the drawing, wherein like reference characters refer to like partsthroughout the several views:

Fig. 1 is a schematic circuit diagram 01' one circuit arrangementembodying the present invention;

Fig. 2 is a schematic circuit diagram illustrating another embodiment ofthe invention; and

Fig. 3 is a characteristic curve or a copperoxide rectifier showing oneeiiective portion which is utilized in the rectifier supplying currentto the main field winding and another efl'ective portion' of therectifier which is utilized in supply- ,ing current to the auxiliaryopposedfleld winding.

In many instances where alternating current generators are employed itis necessary to con- .trol the generated potential within certainlimits.

This is especially true where the generated potential is employed toenergize thermionic vacuum tubes of high frequency signaling systems.Ordinarily, the output voltage of the alternating current generatorvaries with the speed of the generator and it is possible to control theoutput of said generator by controlling the exciting energy inaccordance with changes in the frequency or output voltage of saidgenerator by associating with the output circuit of the generator atuned circuit tuned to a frequency lower than the normal operatingfrequency of the generator. According to the present invention, however,there is provided a novel apparatus for controlling the output of analternator to maintain the output voltage constant irrespective ofspeed, said apparatus consisting generally in an alternator providedwith a main field winding and an auxiliary or differential field windingarranged in opposed relation to said main field winding. The opposedauxiliary field winding is preferably directly connected to the outputcircuit of the alternator through a rectifier of any suitable type, suchas a thermionic vacuum tube type or a copper-oxide type, so that directcurrent passes through said auxiliary field winding to produce thenecessary magnetic flux, while the main field winding is connected tothe output circuit of the alternator through a second rectifier which issimilar to the first one, and through a saturated transformer so thatfor a given increase in the output voltage of the alternator, therectifier associated with the auxiliary field winding providesuni-directional curre'nt'at a faster rate than the rectifier associatedwith the main field winding by reason of the fact that the voltageacross thesecondary of the saturated transformer to which the rectifiersupplying current to the main field winding is connected will notmaterially increase for an internal source after the alternator is inoperation.

A reverse current relay may be employed between the source and therectifier associated with the main field winding to prevent the passageof current through said rectifier when the switch is closed. 4

Referring to the drawing, and more particularly vto Fig. 1, thegenerator or armature shown is of the inductor type embodying a rotor lwhich rotates adjacent to the magnetic field produced by a main fieldwinding 5, and an armature winding 8 which constitutes the output of thealternator. A portion of the output of armature winding 6 is by-passedand delivered to a rectifier I which is preferably of the copper-oxidevtype, although it may be of the thermionic vacuum type, the input ofwhich is connected to the armature winding 6 through a transformerhaving a core 8 and primary and secondary windings 3 and i0,respectively, the primary being to a radio'generator.

aoeaisa connected to the winding 8 and the secondary being connected tothe rectifier I. The output of the rectifier I is connected to the mainfield winding 5 through a reverse current relay Ia, thereby producing amagnetic field which is proportional to the value of'the rectifiedcurrent, the

'latter, however, being limited-by the action of the transformer byreason of the fact that the core 8 of said transformer becomes saturatedat a certain value of the output voltage so that, for any increase of.the output voltage beyond the predetermined value there is no materialincrease in voltage across the secondary l8, thus providing anenergizing current to the main field winding 5 which increases veryslowly for any increase in the output voltage beyond the saturationpoint of the core 8 of the transformer. As pointed out hereinbefore, itmaybe necessary to excite the winding 5 from an independent source,suchas a battery II, for starting the alternator, a switch I: beingprovided to open the .circuit to source II when the necessary current issupplied by the rectifier 1. The main output of. the alternatorconstitutes a supply circuit l3 which is connected to the armaturewinding 8 through a second transformer having a core II and primarywinding 'and secondary windings l5 and I6, respectively.- The core M,however, is unsaturated. The supply circuit l3 may deliver power to theusual devices aboard an aircraft as, for example, to lights, heaters, or

The alternator is shown as of the type designed for aeronauticalinstallation having a stream-lined shell or cover l1 and the rotor 4thereof is adapted to be driven by a propeller shaft i 8 from a winddriven propeller l9. The transformer windings 8 and iii, the rectifierI, the reverse current relay Ia, and the main field winding 5 form onepart of the voltage control system. I

Means are now provided which constitute the other part of the systemforzcontrolling the output voltage of the alternator and, in the formshown,

said means comprise a second rectifier 28 which I is also preferably ofthe copper-oxide type, although it may be of the thermionic vacuum tubetype, the input of-which is directly connected across the armaturewinding 6. The output of the rectifier 20 supplies excitation current toan auxiliary field winding 2| which iswoundin opposed relation to themain field winding 5 and has fewer turns than the main field winding sothat normally the magnetic field produced by the main field windingpredominates. The rectifier 20 is substantially like the rectifier land, therefore, the characteristics are substantially alike. Since,however, the rectifier 28 is connected directly to the armature winding8, an increase in the output voltage beyond the predetermined value atwhich the core 8 becomes saturated will produce a corresponding increasein current in the output of the rectifier 20 and, hence, the fieldproduced by the auxiliary winding 2! will be increased accordingly. Thisphenomenon will be more readily apparent from the curve shown in Fig. 3of the drawing in which the characteristic curve of both rectifiers isshown at a. The saturation point of the core 8 is shown on the curve atb which occurs at a predetermined voltage a: so that the rectifier Ioperates on the lowerportion of the curve from 0 to I: while therectifier 28 operateson the lower portion of the curve and also on theupper portion of the curve from b upward. Thus, it will be seen that afunction of the lower portion of the curve up to the point 11 and fromthe point b, i. e., as the voltage increases beyond a:, the currentincreases relatively slowly as shown by the line in Fig. 3, while thecurrent in the auxiliary winding 2i above a certain voltage increases asa function of the upper portion of the curve, 1. e., from the point bupward. From these characteristics it will be seen that for a givenincrease in the output voltage of the alternator due to increased speed,the field current supplied by rectifier 20 increases at a faster ratethan the current supplied by the rectifier I. Thus, as the outputvoltage of the alternator rises the main field is increased relativelyslowly as compared to the auxiliary field which increases more rapidly.Consequently, since the auxiliary field winding 2i is in opposition tothe main field winding 5, as

.represented by the arrows, the resultant magnetic field of the twowindings will decrease as the output voltage increases due to increasedspeed of the alternator.

It will now be apparent that when the inductor 4 of the alternator isrotated by means of the propeller i9, and a certain amount of residualmagnetism remains in the pole pieces of the main field 5, then as theinductor cuts through the lines of force produced by such magnetism acurrent will be generated in the armature 6. A portion of the currentfrom the armature 6 is rectified by the rectifier l and is then passedto the main field winding 5, thus causing a more intense magnetic fluxto be built up in the field system, and the alternator thereby assumesits normal potential. At the same time, however, a certain amount ofcurrent is rectified in the rectifier 2B and passed through theauxiliary field winding 2|, creating .a magnetic flux therein whichopposes the fiux built up by the field winding 5. For a normal value ofthe output voltage of the alternator, the excitation currents in thewindings and 2| are such that the main field provided by the winding 5predominates, but'upon an increase in voltage above normal, theexcitation current in winding 2i increases at a faster rate than inwinding 5 due to the operation of the rectifiers 20 and 1, respectively,which operate on different portions of their characteristic curves, asshown in Fig. 3, by virtue of the action of the saturated core 8 andtransformer windings 9 and ill in accordance with the invention.Consequently, a constant output voltage is maintained since it will beapparent that the resultant field fiux will decrease if the outputvoltage of the alternator increases above the normal value at which thecore 8 becomes saturated.

In the event that the residual magnetism of the alternator isinsufficient to cause current to be generated in the armature 6 by thestarting of the system, the switch i2 is used, thereby permittingcurrent to flow through the main field winding 5 from the battery H. Thealternator current then builds up as before and switch i2 is opened, thesystem thereafter operating as a unit without the necessity of batteryll being in the circuit.

Referring to Fig. 2, the alternator is the same as that shown in Fig. 1and is provided with main and auxiliary field windings and an armaturewinding, as before, the main difierence being that the armature winding6 is directly connected to the supply circuit i3 instead of beingconnected thereto through an unsaturated transformer in the manner shownin Fig. 1. Except for this change the system operates in the same manneras that shown in Fig. 1.

There is thus provided a novel generating and control system in whichthe output voltage is maintained substantially constant and in which nocircuit interrupting devices are employed during the operating of thesystem so that no electrical disturbances are produced which wouldaffect a radio signaling system employed in the vicinity thereof.

Although only two embodiments of the invention have been illustrated anddescribed, other changes and modifications in circuit arrangement andselection of parts, which will now appear to those skilled in the art,may be made without departing from the scope of the invention. Analternating current generator differing from the type shown may beemployed such as, for example, of the stationary armature and rotatingfield type, or one having a rotating armature and a stationary field.Reference will, therefore, be had to the appended claims for adefinition of the limits of the invention.

What is claimed is:

1. In combination with a source of electromotive force which comprisesan alternator having an output winding, a main field winding and adifferential field winding, a saturated transformer including primaryand secondary windings and having its primary winding connected to saidoutput winding, a rectifier having its input -connected to the secondaryof said transformer and its output connected to said main field windingfor supplying direct current to the latter in proportion to the outputvoltage up to the saturation point of said transformer, and a secondrectifier associated with the output winding and the differential fieldwinding for supplying direct current of such value to said differentialwinding that the combined strength of the two field windings is reducedin response to an increase in 'voltage in the output winding.

2. In combination with a source of electromotive force which comprisesan alternator having an output winding, a main field winding and adifferential field winding, a transformer having primary and secondarywindings and adapted to be saturated above a predetermined voltage inthe output winding, the primary of said transformer being connected tosaid output winding, a rectifier having its input connected to thesecondary of said transformer and its output connected to the main fieldwinding, a battery connected between said rectifier and themain fieldwinding and across the latter, a reverse current relay associated withsaid rectifier and said main field winding for controlling the currentto the battery and to said main field winding, a switch for energizingthe main field winding from the battery, and a second rectifierassociated with the output winding and the differential field windingfor supplying direct current of such value to said differential fieldwinding that the combined strength of the two field windings is reducedin response to an increase in voltage in the output winding.

LAWRENCE A. HYLAND,

